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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.annotation.processing;

import java.util.Set;
import java.util.HashSet;
import java.util.Collections;
import java.util.Objects;
import javax.lang.model.element.*;
import javax.lang.model.SourceVersion;
import javax.tools.Diagnostic;

/**
 * An abstract annotation processor designed to be a convenient
 * superclass for most concrete annotation processors.  This class
 * examines annotation values to compute the {@linkplain
 * #getSupportedOptions options}, {@linkplain
 * #getSupportedAnnotationTypes annotation types}, and {@linkplain
 * #getSupportedSourceVersion source version} supported by its
 * subtypes.
 *
 * <p>The getter methods may {@linkplain Messager#printMessage issue
 * warnings} about noteworthy conditions using the facilities available
 * after the processor has been {@linkplain #isInitialized
 * initialized}.
 *
 * <p>Subclasses are free to override the implementation and
 * specification of any of the methods in this class as long as the
 * general {@link javax.annotation.processing.Processor Processor}
 * contract for that method is obeyed.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 * @since 1.6
 */
public abstract class AbstractProcessor implements Processor {

  /**
   * Processing environment providing by the tool framework.
   */
  protected ProcessingEnvironment processingEnv;
  private boolean initialized = false;

  /**
   * Constructor for subclasses to call.
   */
  protected AbstractProcessor() {
  }

  /**
   * If the processor class is annotated with {@link
   * SupportedOptions}, return an unmodifiable set with the same set
   * of strings as the annotation.  If the class is not so
   * annotated, an empty set is returned.
   *
   * @return the options recognized by this processor, or an empty set if none
   */
  public Set<String> getSupportedOptions() {
    SupportedOptions so = this.getClass().getAnnotation(SupportedOptions.class);
    if (so == null) {
      return Collections.emptySet();
    } else {
      return arrayToSet(so.value());
    }
  }

  /**
   * If the processor class is annotated with {@link
   * SupportedAnnotationTypes}, return an unmodifiable set with the
   * same set of strings as the annotation.  If the class is not so
   * annotated, an empty set is returned.
   *
   * @return the names of the annotation types supported by this processor, or an empty set if none
   */
  public Set<String> getSupportedAnnotationTypes() {
    SupportedAnnotationTypes sat = this.getClass().getAnnotation(SupportedAnnotationTypes.class);
    if (sat == null) {
      if (isInitialized()) {
        processingEnv.getMessager().printMessage(Diagnostic.Kind.WARNING,
            "No SupportedAnnotationTypes annotation " +
                "found on " + this.getClass().getName() +
                ", returning an empty set.");
      }
      return Collections.emptySet();
    } else {
      return arrayToSet(sat.value());
    }
  }

  /**
   * If the processor class is annotated with {@link
   * SupportedSourceVersion}, return the source version in the
   * annotation.  If the class is not so annotated, {@link
   * SourceVersion#RELEASE_6} is returned.
   *
   * @return the latest source version supported by this processor
   */
  public SourceVersion getSupportedSourceVersion() {
    SupportedSourceVersion ssv = this.getClass().getAnnotation(SupportedSourceVersion.class);
    SourceVersion sv = null;
    if (ssv == null) {
      sv = SourceVersion.RELEASE_6;
      if (isInitialized()) {
        processingEnv.getMessager().printMessage(Diagnostic.Kind.WARNING,
            "No SupportedSourceVersion annotation " +
                "found on " + this.getClass().getName() +
                ", returning " + sv + ".");
      }
    } else {
      sv = ssv.value();
    }
    return sv;
  }


  /**
   * Initializes the processor with the processing environment by
   * setting the {@code processingEnv} field to the value of the
   * {@code processingEnv} argument.  An {@code
   * IllegalStateException} will be thrown if this method is called
   * more than once on the same object.
   *
   * @param processingEnv environment to access facilities the tool framework provides to the
   * processor
   * @throws IllegalStateException if this method is called more than once.
   */
  public synchronized void init(ProcessingEnvironment processingEnv) {
    if (initialized) {
      throw new IllegalStateException("Cannot call init more than once.");
    }
    Objects.requireNonNull(processingEnv, "Tool provided null ProcessingEnvironment");

    this.processingEnv = processingEnv;
    initialized = true;
  }

  /**
   * {@inheritDoc}
   */
  public abstract boolean process(Set<? extends TypeElement> annotations,
      RoundEnvironment roundEnv);

  /**
   * Returns an empty iterable of completions.
   *
   * @param element {@inheritDoc}
   * @param annotation {@inheritDoc}
   * @param member {@inheritDoc}
   * @param userText {@inheritDoc}
   */
  public Iterable<? extends Completion> getCompletions(Element element,
      AnnotationMirror annotation,
      ExecutableElement member,
      String userText) {
    return Collections.emptyList();
  }

  /**
   * Returns {@code true} if this object has been {@linkplain #init
   * initialized}, {@code false} otherwise.
   *
   * @return {@code true} if this object has been initialized, {@code false} otherwise.
   */
  protected synchronized boolean isInitialized() {
    return initialized;
  }

  private static Set<String> arrayToSet(String[] array) {
    assert array != null;
    Set<String> set = new HashSet<String>(array.length);
    for (String s : array) {
      set.add(s);
    }
    return Collections.unmodifiableSet(set);
  }
}
